First of all Devendra congrats for such a good score of 62.46 marks and 647 gate score with a 5427 rank in Mechanical engineering in GATE exam!!

So looking at the last year cut-offs you will be able to cross the cut-off in the mechanical engineering department of IIT Bombay, IIT BHU, IIT Gandhinagar.

With this score, you can also get some of the good subjects in other departments like Electrical, Chemical, Civil and Computer science in IIT Roorkee. All departments except Computer Science in IIT Bombay. You can check out the link below for the details about every IITs cut-off or every subject's cut-off in any IIT: https://exams.collegedunia.com/gate/cutoff

This stream changing depends only on your interest and in some of the departments you might not even be allowed to use the mechanical Gate score so make sure you check it and then only apply on the websites of different IITs. You will be notified on the individual IITs website whenever the admission process starts.

Feel free to ask if you have any more queries. All the best!!